A vibration damper assembly has been utilized in the clutch driven member for a motor vehicle power train to control engine induced torsional vibration in the connected elements of the power train. The vibration damper assembly is interposed in the clutch driven member ahead of a manually operated transmission to neutralize the torsional vibrations emanating from the vehicle engine, which vibrations would otherwise cause disturbing impact loads, pulsations, and noises in the transmission and driveline. A vibration damper may also be used for a lock-up clutch inserted into a torque converter for an automatic transmission where the vibrations in the direct drive mode as a result of the lock-up between the torque input and the drive shaft would not be hydraulically dampened by the torque converter vibration damping characteristics.
A conventional vibration damper assembly consists of a clutch hub splined to the output shaft to the transmission, a radially extending integral hub flange, a clutch plate and a spring retainer plate sandwiching the hub flange, and a plurality of compression springs received in circumferentially spaced aligned sets of openings in the plates and flange. The clutch plate and spring retainer plate are rigidly secured together, and the annular friction surfaces are carried on the opposed surfaces adjacent the outer periphery of the clutch plate.
However, special circumstances occur which require a vibration damper having special characteristics so as to control objectionable vibration and/or gear rattle in a transmission which may occur at neutral idle or under engine full load. The present vibration damper provides an extremely low rate of initial deflection to overcome gear rattle problems by effectively suppressing the propagation of torsional disturbances from the engine to the driven elements at idle, and also providing proper frequency tuning at higher engine speeds and loads.
The present invention comprehends the provision of a novel vibration damper assembly for use in an automotive vehicle clutch which provides a variable torsional deflection rate. The vibration damper provides an extremely low first stage torsional spring rate with no damping friction torque and a higher second stage torsional spring rate having an appropriate damping friction torque. The initial low torsional spring rate is provided by a loose spline connection between a clutch hub and a separate hub flange with one or more resilient members provided within the spline connection.
The present invention also comprehends the provision of a novel two-stage vibration damper where the first stage provides an extremely low torsional spring rate and the second stage provides a higher torsional spring rate, wherein the low torsional spring rate may be exerted in either the drive or coast direction or in both directions.
Further objects are to provide a construction of maximum simplicity, efficiency, economy and ease of assembly and operation, and such further objects, advantages and capabilities as will later more fully appear and are inherently possessed thereby.